Pump for hydraulic presses



N. B. HENRY.

PUMP FOR HYDRAULIC PRESSES.

APPLICATION FILED AUG-23. 1920.

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' UNITED STATES NELSON B. HENRY, OF ATLANTA, GEORGIA, ASSIGNOR TO THEMURRAY COMPANY,

PATENT OFFICE.

OF DALLAS, TEXAS, A CORPORATION OF TEXAS.

PUMP FOR HYDRAULIC PRE SSES.

Specification of Letters Patent.

Patented May 10, 1921.

Application filed August 23, 1920. S'erialNo. 405,461.

To all whom it may concern Be it known that I, NELSON B. HENRY, acitizen .of the United States, residing at Atlanta, in the county. ofFulton and State of Georgia,-have invented certain new and usefulImprovements in Pumps for Hydraulic Presses, of which the following is aspecification. 7

My invention is an improvement in pumps for hydraulic presses.

In the pressing of oil seed or analogous material in a hydraulic press,to extract therefrom the maximum amount of oil or fluid, it is desirableto apply the pressure gradually in order that the oil expressed from theseed mass, as the pressure becomes eifective, may have ample time tofind its way to the surface and leave the mass. If the maximum pressureto be applied is, for example, four thousand pounds per square inch, aninitial pressure of say two thousand pounds will be reached inacomparatively short time, in an ordinary oil press in about fourminutes. But this ratiooftime and pressure cannot be maintained inapplying the additional pressure desired, for the obvious reason, that,as the material operated upon becomes more dense, it is necessary toallow a certain time for the expressed oil to find its way out of themass and as the density is increased, by gradual increase of pressure,to the maximum, it is desirable that the press plunger should be movedmore and more slowly until the full pressure is applied andsubstantially all the oil has been expressed. c

- At about midway of the pressing opera-1 tion, say about 2000 poundspressure, the

seed mass has become dense, all airhaving been extruded from the massand the seeds forced intointimate contact and the extrusion of oilproceeds rapidly with the result that the bulk of the mass shrinks bythe amount of oil that passes out of the mass. This shrinkage of masstends to relieve pressure andis immediately counteracted by the movementofthe press plunger which takes up the shrinkageand continuing itsmovement, applies a further increment of pressure to the mass, producingan additional oil extrusion. This process of pressure, partial collapseof the mass tending to relieve pressure and the take up of the shrinkageand establishment of an additional pressure continues until the maximumpressure has been attained and maintained for a sufiicient time, whenthe seed mass has become very solid and no further oil extrusion ispractically possible.

As the pressure in the hydraulic press is increased and the seed massbecomes more dense it is obvious that it will require a continuouslyincreasing power to force a given amount of fluid from the pump to thepress 1n a given time or, in the alternative, that the amount of fluidforced into the press in a given time shall be decreased as theresistance' becomes greater. This eflecthas been attained heretofore byactuating the piston of the hydraulic pump, through a stiff spring,which. as the resistance to the movement of'the piston increased,yielded more and more and, in thisway, the stroke of the piston wasprogressively shortened and less fluid ejected from the pump cylinder asthe piston was reciprocated at a regular power and speed. In this pump,how

ever, at each stroke of the piston the piston spring. was compressed andreleased, causing irregularity of action and a waste of power.

In my present invention'I design to drive my hydraulic pump at a uniformspeed andv positively and, as the resistance to the pumping actionincreases, as the pressure in the press increases, to provide aregularly increasing space by means of an auxiliary cylinder and pistonto receive a regularly in creasing portion of the charge moved by eachreciprocation of the positively driven pump, the difference between thecharge moved at each reciprocation of the piston and the variablyincreasing space of the auxi'liary cylinder being the amount of fluidthat .is forced into the press, which amount is progressivelyandregularly smaller in proportion to the ever increasing density of thecompressed mass, and its consequent lessened.

shrinkage under increaslng pressure. This regularly decreasingproportion of the total charge always moved by the pump piston isaccentuated by the fact that the auxiliary piston 'is preferablycontrolled by a spiral spring and thus moves a distance exactlyproportional to the pressure applied, in the cycles,

- compression spring, abutments on each .10

of each pair being coupled together and moving synchronously but inopposite that is, one pumping iston drawingin a charge of fluid, whilethe other pumping piston is compressing; The auxili'arypistons of thetwo pairs will also be connected through the medium of a single heldbetween suitable piston rod so that the pressure upon one piston will beimmediately transmitted through the elastic medium of the spring, to theother piston.

In the drawings, Figure 1 is a top or plan view of' a pump forhydraulicpresses, embodying my improvement, and Fig. -2 is alongitudinal I sectional elevation on line 4 valves in the well knownmanner. The several cylinders are provided with suitable glands orstufiing boxe s,5, 7 and 17. Cylinders 1 are provided with pistons 6 and8 and cylinders 14 with pistons 16.1 Pistons 6 and 8 are connected attheir outer ends with cross-heads 9, these cross-heads being in turnconnected together by straps 10 and one of the cross-heads beingconnected by a pitman 11 with an eccentric I 111 mounted upon anactuating shaft 112,

carried at one end of the frame 3, and crosswise thereof. The outer endof each. piston 16 is screw threadedand these outer ends carry heads 18which engage and slide upon a guideway 19 formed on the frame 3. Betweenthe heads 18 is interposed a compression spring 20 which may becompressed as desired by means of nuts 21 mounted upon the screwthreaded vportion of pistons 16. By movement of one or both nuts 21 the.initial tension of the spring 20 may be goverened. i

The operation of the pump is as follows: Starting at zero pressure thetwo pumps 6 and 8, moving together butin opposite cycles, 7

alternately force the. fluid to a press or presses connected thereto bythe eduction ducts 12. During the initial stage of operation, theresistance being relatively. small, each iston 6 and 8 displaces itsfullvolume of fluid and forces it to the press, the spring 20 holding thepiston 16 without movement. When the pressure in the press and the consequent resistance to the injection of fluid by the pumps 6 and 8 hasreached a certain stage (determined by the initial set or comand nofluid is bein pression applied to spring 20 by means of nuts 21.) thepressure of fluid as the pistons 6 and 8 move inwardly, begins to takeeffect upon the pistons 16 and causes a slight yielding .of the pistons16 alternately and as the pressure in the pumps increases so 'does themovement of pistons 16 and spring 20. It will be seen that when pistons16 move in their cylinders they provide additional room for a certainportion of the fluid set in motion and displaced by the pistons 6 and 8and that by. this movementiof pistons 16 the amount of fluid forced tothe ress by the movement of pistons 6 and 8 W111 be lessenedprogressively as the pressure increases, so that when a pre-determinedmaximum pressure has been reached, determined by the initial adjustmentof spring 20, the pistons 16 in their movement, will provide space forthe entire amount of fluid displaced by pistons 6 and 8, so that none ofthe fluid will be discharged to the pres? or presses.

This state will continue until a certain amount of the contained oil isextruded, thus relieving the pressure slightly whereupon the balancewill be slightly altered, and piston 16 will move inward slightly thuscausing a small quantity of fluid to be forced to the ress andreinstating maximum pressure. enthe maximum pressure stands for areasonable time without any further compression of the seed mass, theseed mass is completely expressed.

When the maximum pressure is reached forced to the press or presses, theaction 0 the duplex pump is as follows: Piston 6 enters its cyllnder 4:on i the compression stroke when piston '8 is moving outward in itscylinder 4 on the suction stroke. The piston 16 of the casing 2 isforced to the right under pressure of the fluid displaced by piston 6and the left hand head 18 is thus forced to the right. At the sameinstant and to the same extent the piston 16 of the casing 1 movesinward, forced by the movement of piston 16 of casing '2 transmittedthrough the compressed spring 20. When piston 6 is drawn out on its suction stroke the piston 8 is forced in on its compression stroke and thetwo heads 18 and spring 20 move in unison with it. The

spring'thusreciprocates back and forth always under predeterminedcompression so long as the maximum pressure is maintained, no powerbeing consumed in re'compressing a spring which has beenvpermitted toexpand and with absolutely regular action. Should a variation inpressure occur in either cylinder 1, as by reason of the extrusion ofoil or leakage or defective valves in any of the compression cavities,the spring 20 will take. up and rectify the variation by forcing apiston 16 inward toward the cylinder in which the pressure is defective.

The heads 18 with spring 20 constitute, with the pistons 16 in cylinders14, a means for controlling the pressure in cylinders 4 by a regular andprogressive increase to a predetermined maximum and thereafter thecompressed spring 20 without relative movement of its parts willmaintain the predetermined pressure by the exact balance of allelements, while in case of leaks or the like disturbing factors the sring 20 and associated parts will automatically and instantlycompensate, automatically rectifying and balancing a variation inpressure in either or both cylinders 4, instantly and perfectly. Asalready stated, spring 20 when once compressed to the predeterminedamount, will not normally expand or contract but will simply move bodilywith the heads 18 and pistons 16.

I claim as my invention:

1. In a hydraulic pump, the combination of two pairs of cylinders, eachcylinder of a pair communicating at its inner end with its mate and withan inlet and outlet valve and ducts between the cylinders; a piston ineach cylinder, one piston of each pair being coupled to a piston of theother pair and positively actuated in opposite cycles; the other pistonsof each pair being engaged in common by a single compression springtending to force each piston into its cylinder.

2. In a hydraulic pump, the combination of two pairs of cylinders, inaxial alinement, each cylinder of a pair communicating at its inner endwith its mate and with an inlet and an outlet valve and ducts betweenthe cylinders; a piston in each cylinder, one piston of each pair beingcoupled to a piston of the other pair and positively actuated inopposite cycles, the other pistons of each pair being engaged in commonby a single compression spring tending to force each piston into itscylinder.

3. As in claim 1', with adjustable means to impart and retain-anydesired tension to the compression spring.

Signed at Atlanta, Georgia, this 16th day of August, 1920. 4

NELSON B. HENRY.

